How I configure syslog included specific string at /var/log/ltm ?

here is our syslog configuration 

sys syslog {
auth-priv-from notice
auth-priv-to emerg
clustered-host-slot enabled
clustered-message-slot disabled
console-log enabled
cron-from warning
cron-to emerg
daemon-from notice
daemon-to emerg
description none
include none
iso-date disabled
kern-from debug
kern-to emerg
local6-from notice
local6-to emerg
mail-from notice
mail-to emerg
messages-from notice
messages-to warning
remote-servers {
remotesyslog1 {
description none
host X.X.X.X
local-ip X.X.X.X
remote-port 514
}
}
user-log-from notice
user-log-to emerg
}

And i want configure syslog to include specific string on /var/log/ltm 

how I can do this plz help me